The current wave of 3D printers are not based entirely on those patents. They use the same basic principle of extruding plastic filament in layers, but as I und

The current wave of 3D printers are not based entirely on those patents. They use the same basic principle of extruding plastic filament in layers, but as I understand it the details of how to do this effectively were re-engineered by the RepRap project through years of careful experiments. One of the major tricks used to save material cost and printing time - adjustable density infill - is, as far as I know, entirely unique to the RepRap project and the wave of printers building on its work. I think the use of PLA for 3D printing might be solely their doing too.